The invention relates to a plug part for an optical plug-and-socket connection in which there is an axial spring bias on the plug pin, so that when the plug part is inserted into a socket, light transmission is insured, even when there are tolerance deviations, or there is a pull on the cable.
With spring mounted plug pins, it is already known to apply the pin mounting at a certain radial relative position in the housing, in which the most optimal transmission damping is achieved. In spite of a high precision with the encasing of an optical fiber in a plug pin there exist specifically deviations with respect to the concentricity. By measuring out the optimal relative position a high reproducibility of the transmission damping is achieved.
Swiss Patent A-689 316 discloses an optical plug with which the pin mounting is formed as a splined shaft which in six different angular positions is insertable into the inner side of the plug housing, which is formed as a spline bore hub. A spring element in the form of a skeleton-like interrupted hollow cylinder section is directly integrated into the pin mounting. The pin mounting also forms a cable-side terminal part for accommodating the bend protection. Such a one-piece design of the pin mounting, however, is not suitable for all plug types. Furthermore the manufacture of the fiber optic cable with the pin mounting is relatively complicated.
It is therefore the object of the invention to provide a plug part of the initially mentioned type which permits a simple assembly of the plug part and in particular a simple manufacture of the fiber optic cable. Furthermore the plug pin and the plug mounting are to be precisely guided and pre-positioned. According to the invention this object is achieved with a plug part as described below.
The sleeve of this invention in a simple manner forms a means for the rotationally fixed and axially displaceable mounting of the pin mounting as well as for its connection to a cable-side housing terminal part. While the radial position of the pin mounting relative to the sleeve does not play any role, the definitive fixing of the radial relative position is effected on a positioning section on the housing terminal part, which corresponds to a complementary positioning section on the plug housing. The design with the sleeve as a connection element permits also the incorporation of spring elements with different spring forces. Installing the plug at the end section of a fiber optic cable is relatively simple because the pin mounting may be held relatively short and therefore can be handled well.
Particularly advantageously the sleeve is snapped onto the housing terminal part in a rotationally fixed manner. This assembly requires neither tools nor adhesives or the like and the whole unit is easily disassembled again.
For a rotationally fixed mounting in the sleeve the pin mounting may comprise at least one guiding groove which cooperates with a guide element on the sleeve. The spring bias is preferably provided by a helical compression spring which is held in the sleeve between a support shoulder on the pin mounting and an end face of the housing terminal part. At the same time, the sleeve protects the helical compression spring from mechanical effects and from contamination before the final installation of the preassembled unit into the plug housing.
The sleeve may also comprise latching means for securing the housing terminal part in the selected relative position and which is latchable into the plug housing. For this purpose the plug housing may comprise at least two recesses and the latching means may comprise a number of latching tongues which corresponds to the number of possible relative positions of the housing terminal part. In each relative position, at least two latching tongues latch into the corresponding recesses. Of course, a different securement of the housing terminal part in the plug housing would also be conceivable, such as e.g. by screwing, the application of a cotter pin or by an adhesive.
The sleeve is preferably manufactured as a hollow cylindrical bent piece of metal. For this, a sheet metal is first punched out and provided where appropriate with the necessary edgings. Subsequently the sheet metal blank is rolled into a sleeve. Alternatively, the sleeve could be made from a metal tube or as an injection molded part of plastic.
A particularly precise positioning of the pin mounting may be achieved when the mounting comprises a bearing section formed as a truncated pyramid and when the counter bearing on the plug part is formed as a complementary hollow truncated part, the number of side surfaces of the truncated pyramid corresponding to the number of possible relative positions of the housing terminal part. This way, the radial relative position of the plug pin in the uninserted condition, i.e. shortly before contact with the plug counter-piece, is precisely fixed. In the inserted condition, the truncated pyramid lifts from the complementary hollow truncated part and after pulling out returns again into the precise original position. The base of the truncated pyramid may form an abutment which, for limiting the maximum possible spring path on the pin mounting, cooperates with the end face of the sleeve. The positioning section on the housing terminal part may be formed as a hexagon, wherein for example six radial relative positions of the pin mounting in the housing are possible. Accordingly also the truncated pyramid and the complementary hollow truncated part comprise six surfaces.
Independently of the mounting of the pin mounting in the plug housing on a comparable plug part of the known type, further advantages occur when a protective flap, for protecting the end-face of the plug pin, is pivotably and displaceably mounted on a guide path on the plug housing such that upon inserting the plug part into a socket part, the protective flap is movable from a closure position on the end-face of the plug housing into an opening position displaced back relative to the end-face. A guide element fastened on the plug housing simultaneously forms the guide path for the protective flap or is a constituent part of this guide path. This avoids having to work the whole guide path into the plug housing, which in particular with injection molded parts demands complicated tools and an additional material requirement. The guide element may be formed as a U-shaped bow which is snapped onto the plug housing and surrounds this at least partly. Such a bow of sheet material may be easily manufactured and additionally protects the plug part from mechanical effects.
The invention finally concerns also a method for assembly of the plug part. This assembly method permits a simple preassembly of the cable connection units which possibly only are introduced into the plug housing at the customer""s. The measuring out of the optimal relative position is with this effected at the manufacturer""s, wherein by way of a suitable marking for the end assembly no additional measures are required.